The disclosure of Japanese Patent Application No. 2000-236220 filed on Aug. 3, 2000 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
1. Field of Invention
The invention relates to a vehicle controller having a plurality of driving power sources and a starter for starting a specific one of the plurality of driving power sources, and is capable of stopping and starting a specific driving power source based on the prescribed conditions, and a vehicle control method.
2. Description of Related Art
Conventionally, a hybrid vehicle is provided with an engine and a motor generator as driving power sources. In this hybrid vehicle, when the engine torque is not enough with respect to the required driving power, the motor generator is operated as an electric motor to provide the additional torque for the required driving power. On the other hand, when excessive engine torque is generated with respect to the required driving power, the motor generator is operated as a generator to convert the excessive engine torque into electric energy for recovery. Thus, the operating state of the engine can be controlled to achieve excellent fuel efficiency, regardless of the variation in the required driving power.
Japanese Patent Laid-Open Publication No. HEI 9-209790 describes an example of an engine stopping controller of a hybrid vehicle including an engine and a motor generator as driving power sources. The hybrid vehicle described in this publication includes a motor generator, clutch, transmission and differential gear in a power transmission path from the engine to the wheels. If all of the following conditions, i.e., automatic stopping conditions, are satisfied while the vehicle is stopped, the engine is automatically stopped: prescribed time has passed since the vehicle was stopped; the brake is ON; and a battery for supplying electric power to the motor generator has a prescribed charging amount or more. If at least one of the following conditions, i.e., automatic starting conditions, is satisfied while the engine is in the automatically stopped state, the engine is restarted: the brake has been released or the charging amount of the battery has been reduced below the prescribed value.
The motor generator is a rotating machine functioning as a generator or electric motor, and the rotor thereof is coupled to the crankshaft of the engine. Therefore, the following controls are possible: the motor generator is driven with the engine power to generate electric power; and, during coasting of the vehicle, the motor generator is driven with the power of the wheels to generate electric power (regenerative braking control). The following controls are also possible: using the power supplied from the battery, the motor generator is driven as an electric motor to transmit the resultant torque to the wheels; and the engine is started by the motor generator.
Provided that the automatic stopping conditions are satisfied, the engine stopping controller of the aforementioned publication may automatically stop the engine even if the restartability of the engine has been degraded. In this case, the engine may not be able to be restarted, thereby making driving of the vehicle impossible.
The invention is made in view of the aforementioned problems. The invention thus provides a vehicle controller and a vehicle control method capable of preventing the inability to restart a driving power source from being induced.
To achieve the foregoing, a vehicle controller according to a first exemplary aspect of the invention controls a vehicle that includes a plurality of driving power sources for transmitting torque to a wheel, and a starter for starting a first driving power source of the plurality of driving power sources. The first driving power source is stopped when a prescribed stopping condition is satisfied, and the stopped first driving power source is started by the starter when a prescribed restarting condition is satisfied. It is also determined whether startability of the first driving power source by the starter has been degraded. When it is determined that the startability of the first driving power source has been degraded, stopping of the first driving power source is inhibited even when the prescribed stopping condition is satisfied.
According to the first exemplary aspect, when the startability of the first driving power source has been degraded, automatic stopping of the first driving power source is inhibited even when the prescribed stopping condition is satisfied. Accordingly, the inability to restart the first driving power source can be prevented from being induced.
When it is determined, while the first driving power source is stopped, that the startability of the first driving power source by the starter has been degraded, the first driving power source may be started by transmitting power of a driving power source other than the first driving power source to the first driving power source.
According to this structure, when the ability of the starter to start the first driving power source is degraded, while the first driving power source is stopped, the first driving power source is started with the power of the driving power source other than the first driving power source.
When it is determined that the startability of the first driving power source has been degraded due to degradation in the power-generation function of the starter, electric power consumption by the electric driving power source may be suppressed.
According to this structure, electric power consumption by the electric driving power source is suppressed when the startability of the first driving power source has been degraded due to degradation in the power-generation function of the starter. Accordingly, the deficiency of the electric power consumed to start the first driving power source can be avoided.
Moreover, when the startability of the first driving power source has been degraded due to degradation in the power-generation function of the starter, the power-generation function of a second driving power source of the plurality of driving power sources may be used to generate the electric power consumed to start the first driving power source. Thus, the electric power consumed to start the first driving power source can be supplemented.
The starter and the second driving power source may have a function to generate electric power consumed to start the first driving power source. When it is determined that the startability of the first driving power source has been degraded due to degradation in the power-generation function of the starter, the power-generation function of the second driving power source may be used to generate the electric power consumed to start the first driving power source.
According to this structure, a power-generating state of the second driving power source is controlled based on a charging state of the electric power consumed to start the first driving power source. Accordingly, the electric power consumed to start the first driving power source can be more reliably supplemented.
The exemplary aspects of the invention is not limited to the vehicle controller described above. For example, other exemplary aspects of the invention are directed to a vehicle including a vehicle controller, and a vehicle control method.